Combustion regulator

ABSTRACT

A combustion-regulating system for steam boilers including a stem pressure transducer and a steam pressure requirement signal connected to a proportional circuit and integrating circuit, whose output is connected to an input of an amplifier stage which is differentially connected and contained in a first control circuit, whose output is connected with a positioning unit contained in the first control circuit. Said amplifier stage is also connected to an input of a second differentially connected amplifier stage connected in a second control circuit, whose output is connected with a positioning unit contained in the second control circuit. The input of the amplifier stage of the first control circuit is connected to the fuel oil pressure transducer and the input of the amplifier stage of the second control circuit is connected to an air flow sensing device and a fuel oil pressure transducer.

United States Patent Inventor Jerk Gunnar Oldenburg Primary Examiner-William E. Wayner Genarp, Sweden A1t0meyBeveridge & DeGrandi Appl. No. 825,694 Filed May 19,1969 Patented Nov. 2, 1971 Assignee Kockums mekaniska Verkstads AB Malmo, Sweden Priority May 20, 1968 Sweden ABSTRACT: A combustion-regulating system for steam 6794/68 boilers including a stern pressure transducer and a steam pressure requirement signal connected to a proportional circuit and integrating circuit, whose output is connected to an input ffgg g fiffgt of an amplifier stage which is differentially connected and r g g contained in a first control circuit, whose output is connected US. Cl 236/14, with a positioning unit contained in the first control circuit. 2 /15 E, 2 431/76 Said amplifier stage is also connected to an input of a second Int. Cl F23n 1/08 differentially connected amplifier stage connected in a second Field of Search 236/ 15 E, control circuit, whose output is connected with a positioning 14; 431/76 unit contained in the second control circuit. The input of the amplifier stage of the first control circuit is connected to the Reierences cued fuel oil pressure transducer and the input of the amplifier UNITED STATES PATENT stage of the second control circuit is connected to an air flow 3,284,615 11/1966 Yetter 236/15 X ensing de ice and a fuel oil pressure transducer.

PATENTEnunv 2 ml 3,515,997 sum 1 or 6 FIG.!

INVENTORI JERK G. Own/Ema BE VERIDQE J-DE Gym/Di ATTo RM? 75 v PATENTEflunvza Ian SHEET'E'UF 6 w/Q'JERKGO I/vve gm Py: FAK/VERIDGEJDF 904/1 ATTaK/VEy PATENTEnuuv 2 Ian SHEET 3 BF 6 COMBUSTION REGULATOR COMBUSTION REGULATOR The invention concerns a combustion regulator for steam boilers, preferably ships boilers, with one or several burners, to which is assigned a fuel oil control valve with a first control circuit and a fuel oil pressure transducer as well as an air flow control unit with a second control circuit and an air fiow sensing device.

The known types of combustion regulators cannot be used with ships boilers without considerable changes. They are not sufficiently reliable in operation for this area of application. The invention has the purpose of creating a combustion regu lator which can be used above all for ships boilers and this combustion regulator should permit both manual and automatic operation and simulated operation for the control action of the combustion regulator. Furthermore, the regulator is to guarantee ability to perform quick and reliable maneuvers of the ship, whereby great demands are made on its precision and its sensitivity.

The combustion regulator according to the invention therefore derives its advantage in that a steam pressure transducer is connected to a proportionally responsive integrating circuit, in that output from the proportional and integrating circuit is applied as an input to an amplifier stage which is differentially connected and contained in the first control circuit, whose output is applied to control a positioning unit contained in the first control circuit, and in that it is connected as an input to a differentially contained amplifier stage connected in the second control circuit, whose output is applied to control a positioning unit contained in the second control circuit, and in that the input for the amplifier stage of the first control circuit is taken from a fuel oil pressure transducer and the input for the amplifier stage of the second control circuit from the air flow sensing device and the fuel oil pressure transducer.

The invention has been described in the following pages on the basis of the drawings.

FIG. 1 shows a block diagram of a ship's power plant with the combustion regulator according to the invention,

FIG. 2 is a circuit diagram mainly concerning the blocks 18, 23 and 24 in FIG. 1,

FIG. 3 is a circuit diagram mainly concerning blocks -ll in FIG. 1,

FIG. 4 is a circuit diagram concerning a design of block 25 shown in FIG. 1,

FIG. 5 is another design of the block 25 in FIG. 1,

FIG. 6 is a circuit diagram concerning a part of a device for switching over from automatic to manual operation and vice versa of the combustion regulator,

FIG. 7 is a circuit diagram concerning blocks 13 and 14 in FIG. 1, and

FIG. 8 is a circuit diagram concerning a device for a modification of the combustion regulator shown in FIG. 1.

In the block diagram shown in FIG. 1 an installation for propulsion of a ship has been illustrated. This propulsion installation comprises a steam turbine 1 with a main condenser 2. The steam turbine is supplied with steam via a main valve 3, and the steam is fed to this valve from a starboard boiler 4 and a port side boiler, which are of customary type and which are provided with superheaters. The boilers are heated by one or several oil burners. A fuel oil control valve 5 and an air flow control unit 6 as well as a fuel oil pressure transducer 7 and an air flow sensing device 8 are assigned to the starboard boiler 4. Furthermore a positioning unit 9 is assigned to the fuel oil control valve 5, which member is contained in the electronic control circuit 10 of the fuel oil control valve and which can be of any construction which will serve the purpose. In the present instance a positioning unit is electropneumatic. A positioning unit 11 is also assigned to the air flow control unit 6, which unit is contained in the electronic control circuit 12 of the air control unit and which might be of any construction that will serve the purpose. This positioning unit too is electropneumatic in the present instance. In certain cases the starboard boiler 4 can be equipped with a device 13 which, together with an electronic circuit 14, senses the oxygen content of the escaping flue gases and which influences the control circuit 12 of the air flow control unit 6 according to this content in such a manner that one will obtain the smallest possible surplus of oxygen. The port side of the installation is comprised of the same components 4-14 and has been shown here only as a single block 15. The steam produced by the port side 15 and the starboard side 4 is fed via pipes 16 and 17 to the main valve 3. A steam pressure transducer 18, connected to pipe 17, produces an electric output signal proportional to the steam pressure. The main valve 3 is regulated from the bridge of the ship by means of a control system equipped with a positioning unit 19. This control system also produces a signal for the requirement of steam pressure. The adjusting element 19 is operated by means of a further adjusting element 21 which is controlled by a quick action release system 22 for the main engine (designated as Trip System among technicians in this field. This system produces a rapid decreasing of the steam pressure signal.

The described combustion regulator of the present invention obtains its input values from the systems 20 and 22 and from the steam pressure transducer 18. These values are fed to a proportional and integrating circuit 23. But let us emphasize that the steam pressure requirement signal is fed by system 20 to the integrating circuit 23 via a differentially connected amplifier stage 24, that the signal from the steam pressure transducer 18 is an error signal proportional to the difference between a set value adjusted by means of a potentiometer P1 and the true value obtained by means of a measuring element of the steam pressure, and that the signal from system 22 is obtained upon closing a contact that can be controlled by a relay RE3. The output signal obtained from the proportional and integrating circuit 23 first of all is fed to a device 25 which serves for the firing or stopping of one or several burners in both boilers successively one after the other or for opening of a steam release valve. Device 25 naturally will be utilized only when the boiler load is extraordinarily low.

In the following paragraphs the components contained in the actual combustion regulator are described in more detail. FIG. 2 shows blocks 18, 23 and 24 in their details and also a device for the simulated operation with the combustion regulator. Essentially this device consists of an operational amplifier I3 connected for proportional and integrating operation; it will be described in more detail below. As already mentioned. the desired value of the steam pressure is adjusted by means of the potentiometer P1, one of the connections of which is connected via a resistance R1 to a voltage input 0V and the other connection of which is connected via a resistance R2 to a voltage input l5 v. The sliding contact of the potentiometer P1 has been connected partly to a connection of a steam pressure transducer 26 and partly to the one connection of a steam pressure gauge 27. The measuring element 26 produces an electric signal which is proportional to the actual value of the steam pressure. The other connection of the measuring element 26 has been connected to the input of an operational amplifier 12 via a resistance R11 and a relay contact REI, which is shown in FIG. 2 in its position for automatic operation with the combustion regulator. A Zener diode Z1 and two resistances R3 and R4 connected in parallel have been switched in via the connection of the measuring element 26. The other connection of the steam pressure gauge 27 has also been connected to supply input to the operational amplifier l2 via the resistance R11. The operational amplifier I2 is connected for proportional and integrating operation and has a second input (or plus input terminal) connected via a resistance R12 to a voltage input OV. The operational amplifier I2 has furthermore been connected to a voltage input OV via a condenser C5, whose connection facing away from the voltage input has been connected via a resistance R38 to the output of the operational amplifier l2. The output of the amplifier I2 is connected with a first or minus input partly via a diode D5 and partly via a condenser C4, which is connected in series with a resistance R17 connected in parallel with a condenser C3. The minus input of the operational amplifier 12 has furthermore been connected via a condenser C2, a resistance R10 and another resistance R9 to the output of another operational amplifier 11. The three last mentioned components are connected in series. The operational amplifier 11 is connected as a differential amplifier and it will thus produce at its output a signal proportional to the difference between the input signals. The output of the amplifier I1 is connected via a resistance R8, connected in parallel to a diode D3, with one of the inputs of the amplifier, and this input is connected with the other input of the amplifier 11 via two series-opposed-connected Zener diodes Z2 and 23 to a voltage input series-opposedconnected and via two diodes D1 and D2, connected in parallel and facing each other. The latter input has been connected to a voltage input V via a resistance R7. One of the inputs of the operational amplifier I1 furthermore has been connected to the system 20 via a resistance R6, while the other input of the amplifier is connected to the system 20 via a resistance R5. The connection between resistances R9 and R is connected with a voltage input OV via a contact which can be controlled by means of the above mentioned relay RE3. The minus input of the operational amplifier I2 has been connected to a voltage input 0V via a resistance R and a diode D4. The connection between resistance R15 and diode D4 has been connected to a voltage input l5 v. via a resistance R14 and to a voltage inlet -15 v. via a resistance R14 and to a voltage inlet +15 v. via a resistance R13. Furthermore, the minus input of the operational amplifier I2 has been connected to another part of the combustion regulator via a resistance R16, and this part will be described in more detail further below.

The proportional and integrated signal, corresponding to the requirement of steam pressure and obtained as the output of the operational amplifier I2, is fed via a diode D7 to the sliding contact of a potentiometer P2 (FIG. 3). The one connection of the potentiometer P2 has been connected to the circuit arrangement, shown in FIG. 3, while its other connection has been coupled with an identical circuit arrangement for the port side of the installation. The potentiometer P2 serves for the establishment of an equilibrium between the port side and the starboard side. The one connection of the potentiometer is connected to the minus input of a differentially connected operational amplifier I50 via a resistance R52. This operational amplifier I50 is contained in the operational circuit for the fuel oil control valve 5. The minus input of the operational amplifier I50 has been connected to the plus input of said amplifier via two diodes D51 and D52, which are oppositely connected in parallel. The plus input of the operational amplifier I50 has furthermore been connected to a voltage input 0V via a resistance R53 and the amplifier itself is connected to a voltage input OV via a condenser C51, whose connection facing away from the voltage inlet is connected to the output of the operational amplifier I50 via a resistance R103. The minus inlet of this amplifier is connected to a voltage inlet 1 5 v. via a resistance R51, which determines the minimum oil pressure, and to a voltage input +15 v. via a resistance R50 and a switch contact. Upon closing of the contact therefore, the resistance R50 is connected to the minus input of the amplifier I50, whereby the oil pressure is raised somewhat. The minus input of the amplifier I50 is furthermore connected to one of the connections ofa measuring element 28 for the oil pressure via a resistance R56 and the relay contact RE2, which measuring element provides an output signal proportional to the prevailing oil Pressure. The other connection of the oil pressure measuring element has been connected to a voltage input 0V, and between the connections two series-connected resistances R54 and R55 as well as a Zener diode 250, connected in parallel with the latter, have been switched in. The connection between resistance R56 and relay contact RE2 has been connected via resistance R65 to the plus input of an operational amplifier I51 and via two series-connected resistances R60 and R61 to a voltage input 0V and finally via a contact MS to one of the connections of an oil pressure gauge 29. The other terminal of gauge 29 has been connected to a voltage input 0V. The minus input of the operational amplifier I50 has also been connected to the emitter of a transistor T50 via a condenser C50 connected in parallel with a resistance R57. The output of the operational amplifier is coupled via a diode D53 with the base of transistor T50, while the collector of the transistor is connected to a voltage input l5 v. via a resistance R58. The emitter of transistor T50 is connected via a resistance R59 to the voltage input l5 v. and via a contact MS to a positioning unit 9, whose other terminal has been connected to a voltage input OV. The contacts MS mentioned in this connection serve for the changeover of the circuit to manual operation, although they are shown in the position for the automatic operation of the circuit. Those parts of the circuits which upon the changeover of the contacts MS are switched on are described in more detail further below. What has been said about the contacts MS is also valid for contacts NS described hereafter.

The operational amplifier 151, which has been mentioned previously, is differentially connected just like the operational amplifier 150, but it is contained in the operational circuit of air valve 6. The plus input of the operational amplifier 151 has been connected via two diodes D54 and D55, facing each other and connected in parallel, to the minus input of the amplifier, and via a resistance R67 to a voltage input 0V. The amplifier I51 itself is connected to a voltage input 0V via a condenser C53, whereby the terminal of the condenser C53, facing away from the voltage input, is coupled via a resistance R104 with the output of the amplifier. The minus input of amplifier I5] is connected via a resistance R64 to a voltage input l5 v. and via a resistance R62 to a voltage input +15 v.. and furthermore via a resistance R73 to sliding contact of a potentiometer P52, one of whose terminals is connected to a voltage input 0V and whose other terminal leads to a connection of an air pressure gauge 30. The other connection of this gauge leads to a voltage input OV. The other terminal of the potentiometer P52 furthermore has been connected via a relay contact REZ to a connection of an air pressure flow measuring element 31, which provides an output signal which is proportional to the air flow to the boiler. The other terminal of the measuring element has been connected to a voltage input 0V and via the terminals, a Zener diode 253 and three series-connected resistances R77, R78 and R79 have been switched in, whereby a resistance R75, which is series-connected with Zener diode Z54, has been connected in parallel with the resistances R77 and R78. Furthermore, a resistance R76, which is connected in series with a Zener diode 255, has likewise been connected in parallel with the resistances R77 and R78. Let us emphasize here that potentiometer P52 serves for an equalization of the air pressure flow in relation to the oil pressure or vice versa. The minus input of the operational amplifier I51 has been coupled furthermore via a condenser C52, connected in parallel with resistance R74, with the emitter of a transistor T51, whose base has been connected to the output of the operational amplifier I51 via a diode D50. The collector of the transistor has been connected to a voltage input -15 v. via a resistance R84, which input is connected to the emitter of transistor T51 via a resistance R85. The emitter is connected to the positioning unit 11 via a contact NS, whose other terminal has been connected to a voltage input OV. The emitter of transistor T51 has furthermore been connected to the minus input of the operational amplifier I50 via a Zener diode 251 which serves to lower the oil pressure and thus the oil supply whenever positioning unit 11 is operated by an abnormally large signal indicating an insufficient air supply. Similar measures have been taken in the case of a too rapid and too strong increase of the oil pressure, which measures consists in that the input of the positioning unit 9 is connected to the plus input of the operational amplifier I51 via a resistance R69, a condenser C54 and a diode D56. The connection between diode D56 and condenser CS4 has been connected to the connection between resistances R60 and R62 via a resistance R68. In the case of a rapid growth of the signal to the positioning unit 9, condenser C54 is thus charged and then an increasing of the output signal from the amplifier I5l is obtained. Let us stress here that condenser C54 will be discharged via resistance R68.

In principle, the part of the combustion regulator described hitherto is sufficient for a perfect and precise regulation of the oil and air supplies to the boiler for the purpose of producing steam according to a certain minimum requirement and a certain maximum requirement. However, there are occasions when the boiler load drops below the smallest standard value and in such cases it will be necessary either to reduce the production of steam in some way or another to a value below the standard minimum, or else the excess must be eliminated in some way or another, for example through releasing steam from the system. According to the circuit shown in FIG. 4, one or several of the burners for the boiler can be shut down one after the other whenever this is necessary. The circuit shown in FIG. 4 consists of an operational amplifier I54 whose minus input is connected via a resistance R96 to the sliding contact of the potentiometer P2 and via a Zener diode Z52 to the output of the amplifier. The output of the amplifier is connected to an amplifier plus input via a resistance R99. Furthermore, the plus input is connected via a resistance R97 and a resistance R98 to a voltage input V. The connection between resistances R97 and R98 is connected to a voltage input l v. via a resistance R95. The output of the operational amplifier I54 is connected via a resistance R101 to the base of a transistor T54, whose emitter is connected to a voltage input 0V and its collector to a relay coil RE3 (4), whose other end is connected to a voltage input l5 v. The collector of transistor T54 is further connected via a diode DA to a voltage input 1 5 v. If the demand signal from the operational amplifier 12 drops below a certain value, the relay RE3 will thus respond and will shut down the burner assigned to the operational amplifier I54. Upon continuing reduction of the demand signal, a second circuit similar to that for operational amplifier I54 will shut off another burner. Whenever the demand signal increases again, the burners are again ignited. Instead of the circuit described in connection with FIG. 4, one can use the circuit shown in FIG. 5, which serves to increase steam load of the system. As can be seen from FIG. 5, the circuit serves to feed a positioning unit 50. One of the terminals of the adjusting member has been connected to a voltage input 0V and its other terminal to the emitter of a transistor T1. The emitter of the transistor has furthermore been connected to a voltage input 1 5 v. via a resistance R22 and this voltage input is connected via a resistance R21 to a collector of the transistor. The base of transistor T1 is connected via a diode D6 to the output of the operational amplifier I2. Let us stress here that the resistances R38 and R39 (FIG. 2) can be omitted, whenever the circuit shown in FIG. 5, and which however is not particularly economical, is used instead of the circuit shown in FIG. 4.

The combustion regulator of the invention is also intended for simulated operation. Such an operation is accomplished through the changeover of the switch S shown in FIG. 2 by coupling the voltage input l5 v. with the relay coils RBI and RE2, the other ends of which are connected to a voltage source of +l 5 v. or a voltage source of 0V. The contacts RE] or RE2 of the relays REl and REZ are thus changed over from the position shown in the figures into their other position, as a result of which the measuring elements or measuring converters 26, 28 and 31 together with their circuits are disconnected from the regulator and the part of the circuit shown in FIG. 2 and comprising the operational amplifier I3 is switched in. This operational amplifier is connected as an integrating amplifier and its minus input is connected via a resistance R19 to a voltage input 0V and via a condenser C6 to the output of the amplifier. The condenser C6 is connected in parallel with two series-connected Zener diodes Z4 and Z5 facing each other. The operational amplifier I3 is connected to a voltage input 0V via a condenser Ca, whereby the terminal of the condenser facing away from the voltage input is connected to the output of the amplifier via a resistance R39. The plus input of the amplifier is connected to the output of the operational amplifier I2 via a resistance R20 and via a resistance R18, connected in parallel with a condenser C8, and a switch S2 to a voltage input CV with the switch in the position shown and with the switch in its other position it is connected to a voltage input 15 v. It is noted that resistance R20 represents a certain oil load and resistance R18 a certain steam requirement, whereby condenser C8 represents the steam pressure drop at the superheater. With the switch S2 in the position shown, the resistances R20 and R18 give a predetermined low steam load and with the switch S2 in the other position a predetermined high steam load is simulated.

The combustion regulator of the present invention is also fitted for the changeover from the automatic to manual operation and vice versa. For the changeover of the regulator to manual operation, a switch will be operated with which contacts MS and NS are changed over from the position shown into their other position. The device provided for this purpose is shown in FIG. 6, where besides the contacts MS and NS, contacts MP and NP also occur, which belong to the installation on the port side. The connection B in FIG. 3 leads to connection B in FIG. 6, the connection C in FIG. 3 leads to connection C in FIG. 6, and the connection D in FIG. 3 leads to the connection D in FIG. 6. The connection E in FIG. 3 leads to the connection E in FIG. 6, connection F in FIG. 3 leads to connection F in FIG. 6, and connection G in FIG. 6 leads to connection G in FIG. 2. The circuit shown in FIG. 6 comprises two differentially connected operational amplifiers I4 and I5. In the case of changeover of the contacts MS and NS and thus of contacts MP and NP, leading to the port side, the contacts will assume their position which is opposite the position shown in the drawing, as a result of which, among other things, the measuring gauges 29 and 30 are switched away from the measuring circuits and are connected together with a manually operated circuit for the oil control valve and a manually operated circuit for the air flow control unit, to the regulator. Also, the operational amplifier I4 and IS with their circuits are connected to the regulator. Also, the operational amplifier l4 and 15 with their circuits are connected to the regulator. As becomes clear from FIG. 3, the positioning unit 9 will be connected to the emitter of a transistor T52, the base of which is connected to the sliding contact of a potentiometer P50, one of whose terminals is connected to a voltage input 0V and the other of its terminals with a voltage input -15 v. The emitter of the transistor T50 is connected to the voltage input 0V via a resistance R70. The voltage input 15 v. is connected via a resistance R71 to the collector of transistor T52 and via a resistance R72 to the emitter of transistor T52. The emitter of the transistor T51 is connected via a resistance R86 with the voltage input 0V. The adjusting element 11 will be coupled with the emitter of a transistor T53, whose base is connected to the sliding contact of a potentiometer P51, one of whose terminals is connected with the voltage input 0V and the other of its terminals with the voltage input l5 v. II Voltage input l5 v. II is connected via a resistance R87 to the collector of transistor T53 and via a resistance R88 to the emitter of transistor T53. The gauges 29 and 30 will be connected to the output of the operational amplifier I5. Output and minus input of the operational amplifier l5 are connected with one another via a resistance R37. The minus input furthermore will be connected via a resistance R32 and a contact MS to the connection C, via the resistance R31 and a contact MS to the connection E, via the resistance R30 and a to MP to a port side con nection and via resistance R29 and a contact NP to another port side connection. The plus input of the operational amplifier 15 will be connected via a resistance R33 and a contact MP to a port side connection, via the resistance R34 and a contact MP to another port side connection, via the resistance R35 and a contact NS to the connection D and via the resistance R36 and a contact MS to the connection F. Plus input of amplifier I5 is furthermore connected via the resistance R40 to a voltage input l5 v. and via a resistance R41 to a voltage input OV. The operational amplifier I is connected with a voltage input OV via a condenser C10. Furthermore, the minus input of operational amplifier I5 is connected via the resistance R32, the contact MS and the resistance R23 with the minus input of the operational amplifier l4. The minus input of the operational amplifier I4 is connected via a resistance R28 to the output of said amplifier and via a resistance R24, the contact MP and the resistance R30 with the minus input of the operational amplifier IS. The plus input of the operational amplifier I4 is connected via a resistance R25 to the connection B, via the resistance R26 with the port side connection and via a resistance R27 to the voltage input 0V. The operational amplifier I4 is connected via a condenser C9 to a voltage input 0V. At the gauges 29 and 30 the difference between the adjusted value given by the potentiometers PS0 or PS1 and of the automatic output to the positioning unit prevailing upon changeover will be shown by means of the circuits, mainly the operational amplifier l4 and 15, described in connection with it, as a result of which 'a changeover of the system from automatic operation to manual operation becomes practically completely free of shock.

One can also connect blocks 13 and 14 to the abovedescribed combustion regulator. These blocks serve for the sensing of the degree of combustion of oxygen achieved and for the adjusting of the air flow control unit corresponding to the measured degree of combustion of oxygen. In FIG. 7 the blocks 13 and 14 have been shown in more detail and are connected by means of switch S3 to the remaining circuit. The circuit shown in FIG. 7 comprises a measuring transducer 40, which puts out a signal that is proportional to the sensed degree of combustion of oxygen. A Zener diode Z58 and a resistance R89, connected in parallel with the former, are connected via the connections of the measuring transformer. One of the terminals of the measuring transducer furthermore is connected to a voltage input OV, while its other terminal is connected via a resistance R92 to the minus input of an operational amplifier I53 which is coupled as an integrating amplifier. The minus input of the operational amplifier is furthermore connected via a resistance R91 to a sliding contact ofa potentiometer P53, one of whose connections is connected to the voltage input 0V and whose other connection is connected via a resistance R90 to a voltage input +15 V. The operational amplifier I53 is connected via a condenser CS7 to a voltage input 0V, whereby the terminal of this condenser facing away from the voltage input is connected via a resistance R106 to the output of the amplifier. Furthermore, the output of the amplifier is connected via a condenser C56, connected in parallel with a Zener diode 257, to the minus input of the amplifier. This minus input is connected to the output via a resistance R93 and the switch S3. The output signal from the amplifier is conducted via a resistance R66 to the plus input of the operational amplifier I51 and via a resistance R63 to the minus input of this operational amplifier. In this manner the signal from the circuit shown in FIG. 7 will influence the adjustment of the air flow control unit 6.

If the two measuring converters 28 and 31 are not linear, it will be necessary to change the circuit shown in FIG. 3 in the manner illustrated in FIG. 8. For example, in case the air flow sensing unit 31 is not linear, it will be connected via the operational amplifier I52, connected as a differential amplifier and shown in FIG. 8, to the operational amplifier I51. A Zener diode Z56 and in parallel with these, two series-connected resistances R82 and R83 are switched in via the terminals on the measuring converter 31. The connection to the measuring converter is coupled with the voltage input 0V and the other connection is connected via a resistance R80 with the minus input of the operational amplifier I52. The plus input of the operational amplifier I52 is connected via a resistance R81 with a zero voltage input, while the actual operational amplifier is connected via a condenser CS5 with a zero voltage input 0V, whereby the side of this condenser facing away from the voltage input is connected via a resistance R105 with the output of the operational amplifier I52. Whenever the circuit 5 junction between the resistance R78 and Zener diode Z55.

The terminals designated by A in the drawings are switched into a supervisory installation with an alarm which immediately shows an error in any one of the outer circuits of the positioning units and the measuring converters.

SUMMARY OF OPERATION Oil-fired steam boilers for different types of steam-consuming applications such as propulsion machinery, turbogenerators, cargo pumps, steam supplies, etc. require steam generation controls in which the steam pressure output from the boiler is preferably maintained at a constant value sensed as a steam pressure and transmitted as a control signal to a combustion regulator. If the boiler is of the single-pressure type, this combustion regulator will operate as a PI-regulator and if its is of the double-pressure type it will operate as a PlD-regulator, in either case employing an integrated pressure signal representing a steam requirement or demand. The difference between the output signal of the steam pressure transmitter and a set value is fed into the PI-controller whose output (power demand) is a measure of the fuel oil demand of the boiler.

This power demand signal is fed to the fuel oil controller, or, if two boilers are used, the two steam outputs are connected to a common steam line so that the fuel oil demand will be equal for both boilers. The power demand signal is fed to one fuel oil controller for each boiler by way of a balancing potentiometer for adjustment of the balance between the two boilers. The fuel oil controller is a P-regulator with a time lag for controlling the fuel oil control valve and employs a fuel oil pressure feedback such that the fuel oil pressure is controlled in accordance with the power demand signal. The fuel oil pressure is detected and fed to the air controller which is also a P- regulator with time lag.

The air controller regulates air supply for complete burning of the fuel oil in the boiler and employs an air flow feedback. The air supply is controlled in various ways, as by air dampers controlling the air flow at the pressure side of the fan, inlet vanes controlling the air flow at the suction side of the fan, or by fan speed control. For immediate control of air flow to the boiler in response to a stepped increase in fuel oil delivered to avoid a transient air deficiency causing improper combustion two differentiating networks are used in which one is con nected in the power demand signal path to the input of the air controller and the other in the input signal path to the fuel oil control valve and is connected as an input to the air controller. The differentiating networks are connected into the air controller circuit only during increases in fuel oil demand actuating the fuel oil control valves.

Improved performance for the PI-controller during maneuvering of a ship is obtained by the use ofa feed forward signal from the main turbine control system which is approximately proportional to the propulsion power ordered (essentially the steam consumption rate) and is fed to the Pl-controller by way of a differentiating network so that an output signal proportional to this feed forward signal is obtained.

Whenever a main turbine or other steam consumer is cut off suddenly, the steam pressure will rise very rapidly because of the large amount of heat energy stored in the heat exchanger as temperature differential to maintain flow from heat source to the water. In the case of a boiler with a superheater the normal pressure differential across the superheater disappears and also causes a step increase in boiler pressure. Such increased steam pressures at turbine cutoff are minimized as far as possible by very rapidly decreasing the power demand signal according to the derivative of the feed forward signal, made effective as by the closing of a switch activated by the trip signal which terminates turbine operation.

SUMMARY OWPERATION The combustion-regulating system outlined above will now be described more in detail with reference to the circuits shown in FIGS. 2, 3 and 7, operation of circuits 4, 5, 6 and 8 being hereinbefore specified. A desired value of the steam pressure in the pipeline 17 (FIG. l) is set by means of the potentiometer P1 in FIG. 2. The steam pressure in the pipeline 17 (FIG. 1) produces a corresponding electrical signal from the steam pressure transducer 26. If the desired value set by means of the potentiometer P1 differs from the actual value obtained from the transducer 26 a differential signal occurs at the minus input of the operational amplifier I2. This differential signal is both proportioned and integrated for generating a requirement signal on the output of the operational amplifier I2. This requirement signal is fed via the potentiometer P2 and resistor R52 to the minus input of the operational amplifier I50 provided in the fuel oil control circuit I2, and the output signal of said input determines the degree of opening of the fuel oil control valve and thus the oil supply to the burners in the boiler 4. The actual value of the fuel oil pressure is obtained from the fuel pressure transducer 28 and the output signal of said transducer is applied to the operational amplifier I50 via resistor R56, a difference between the actual value and the desired value producing a signal at the output of the operational amplifier I50, said signal being applied to the fuel oil control valve 5 via transistor T50. The fuel supply to the boiler 4 should be proportional to the actual value of the fuel oil pressure, for which reason the operational amplifier I51 arranged in the air flow regulating unit is connected to the output of the fuel oil pressure transducer 28 via a resistor R65. The actual value of the fuel oil pressure thus also represents the desired value of the air supply. The actual value of the air supply is obtained from the air flow sensing device 31 and the signal therefrom is applied to the input of the operational amplifier I51 via resistor R13, a difference between the desired value and the actual value producing an output signal from the operational amplifier I51, which is applied to the air fiow regulating unit 6 via transistor T5] for increasing or reducing the air supply.

To accelerate the controlling function hitherto described, which permits controlling the amount of fuel and air supplied to the boiler 4, the signal applied to the oil control valve 5 from the operational amplifier I50 via transistor T50 is applied to the input of the operational amplifier I51 via resistor R69, capacitor C54 and diode D56 so that the operational amplifier I51 receives preliminary information that the fuel oil pressure to the boiler will be altered. It should be observed that the diode D56 serves to prevent the control by this signal at decreasing fuel oil pressure. This is simply due to the fact that it is desirable to prevent smoke puffs from arising, which in accordance with the present invention occurs in that the air supply at possible increases of the fuel oil pressure is always kept slightly higher until stability has been established. This desideratum is further stressed by the connection between the input of the member 11 and the input of the amplifier I50. This connection also comprises the Zener diode 251. An input signal to the operational amplifier I50 which orders a heavy increase of the fuel oil pressure will thus be limited by means of the connection between the member 11 and the input of the operational amplifier I50 via the Zener diode Z51 in such a way that the output signal from the operational amplifier ISO is restricted in relation to the output signal from the operational amplifier I51, whereby it is impossible to supply more fuel oil than can be burned by the air supplied.

The control of the air supply can be made still more precise by the connection of the circuit shown in FIG. 7, which influences the desired value of the air supply at the input of the operational amplifier [50 since the circuit shown in Flg. 7 is connected to the plus input of the operational amplifier I51 via resistor R66 or alternatively to the minus input of the operational amplifier I51 via resistor R63. The measuring transducer 40 delivers a signal which is proportional to the oxygen content of the exhaust gases and thus indicates the actual value of the oxygen content of fhe exhaust gases This actual value signal is applied to the minus input of the operational amplifier I53 which is connected for integration, and a desired value set by means of the potentiometer P53 is also applied to the minus input of the operational amplifier I53. When the desired value and the actual value differ a signal occurs on the output of the operational amplifier I53 which signal in turn influences the desired value of the air supply at the input of the operational amplifier I51. At the control of the air supply attention is thus paid not only to the fuel oil amount supplied to the boiler 4 but also to the oxygen content of the exhaust gases.

When the combustion-regulating system hereinbefore described is utilized in a steam-generating plant of a turbine (FIG. 1) which is connected to the pipeline 17 via the main valve 3 a steam pressure requirement signal is fed from the steam pressure requirement signal transducer 20 via the differentially connected operational amplifier II, at the output of which there occurs a signal corresponding to the degree to which the main valve 3 is opened. This signal is supplied to the operational amplifier I2 via resistors R9 and R10 and capacitor C2 and will thus affect the requirement signal. If the requirement for steam quite suddenly ceases, for instance at a so-called trip of the turbine 1, a signal is fed from the rapid function switching device 22 of the relay Re3, which signal makes the relay Re3 operative and closes the contact thereof shown in FIG. 2 so that the output signal from the operational amplifier I2 will be zero, whereby the requirement signal from the operational amplifier I2 will be small and both the oil and air supply is rapidly reduced.

IcIaim:

1. In a system for regulating combustion for a steam boiler including at least one burner supplied by a fuel oil control valve operated by a first control circuit responsive to fuel oil pressure and having an air flow control unit operated by a second control circuit including an air flow sensing device: means generating a signal indicating a desired steam pressure, steam pressure transducer means for generating a signal indicating an actual steam pressure, a proportional and integrating circuit responsive to the difference between a signal indicating the actual steam pressure and said signal indicating the desired steam pressure, a first control circuit including a differentially connected amplifier device connected to receive the output of said integrating circuit, a positioning unit responsive to said first control circuit connected for controlling a fuel valve in response to output from said amplifier device, a second differentially connected amplifier device comprising a second control circuit having one input taken from said output of the first control circuit and a second input responsive to the output of said proportional and integrating circuit, a second positioning unit connected for response to said second control circuit and in control of air flow, a fuel oil pressure detecting transducer connected to a fuel supply to the boiler, an air flow sensing device connected to an air supply to the boiler the input of said first control circuit being responsively connected to said fuel oil pressure transducer and the input of said second control circuit being connected for response to the air flow sensing device and to the fuel oil pressure transducer.

2. In a system according to claim I differentially connected amplifier means connected for response to a steam pressure requirement signal and supplying said signal to said proportional and integrating circuit for proportional effect on the output from said last-named circuit.

3. In the system of claim 1, rapid switching means under control of a trip signal from a turbine system supplied by said steam boiler for supplying a time-derivative signal to said proportion and integrating circuit when the steam supply to said turbine engine system is shut off by a safety system.

4. In a system according to claim I, said differentially connected amplifiers comprising operational amplifiers connected for output according to the difference between input signals and said proportional and integrating circuit comprising an operational amplifier connected for producing a proportional and integrated signal output.

5. In the system of claim 1, said first control circuit having said amplifier device connected for response to the output signal from said second control circuit by way of zener diode means to the output signal from the first control circuit according to sensed air flow below a set value.

6. In the system of claim 1, said second control circuit having input to said amplifier device thereof derived from an input signal to said positioning unit controlling fuel delivered through RC network means to provide a differentiated signal.

7. in the system of claim 1 means connected to said boiler for detecting oxygen content of flue gases and means responsive thereto for varying the operation of the flow control unit to reduce air flow according to oxygen detected, said means operating to provide an input to said second control circuit.

8. [n a system according to claim 7 said means for detecting oxygen comprising an integrator-connected operational amplifier having a feedback circuit including Zener diode means for limiting the magnitude of signal applied to the second control circuit.

9. ln a system according to claim 1, transistor amplifier means connected to the output for said control circuits to erthance the signals to said positioning units.

10. ln the system of claim I, manually operable control signal generating means connected to each said control circuit, including further differentially connected operational amplifier means responsive to said manually operable means supplying input for said integrating circuit.

11. In the system of claim 10, means connecting said manually operable means such that output from one said further operational amplifier means provides a gauge-operating signal and the other said further operational amplifier means provides input to said integrating means.

12. In the system of claim 1, said second integrating circuit means for simulating a steam demand signal and generating a fuel control signal comprising amplifier means responsive to said output of said integrating circuit.

13. in the system of claim 1, comparator-connected operational amplifier means connected responsively to the output of said proportional and integrating circuit, and amplifier means connected for response to the output of said comparator-connected amplifier means, for supplying a rapid start or stop signal for a burner, and relay means responsively connected thereto to furnish start or stop actuation power.

14. in the system of claim 1, amplifier means for controlling an actuation signal to a further positioning unit, being connected for response to output from said proportional and integrating circuit and supplying an actuating signal for a steamdumping valve upon developing a predetermined output and a steam-dumping valve connected thereto. 

1. In a system for regulating combustion for a steam boiler including at least one burner supplied by a fuel oil control valve operated by a first control circuit responsive to fuel oil pressure and having an air flow control unit operated by a second control circuit including an air flow sensing device; means generating a signal indicating a desired steam pressure, steam pressure transducer means for generating a signal indicating an actual steam pressure, a proportional and integrating circuit responsive to the difference between a signal indicating the actual steam pressure and said signal indicating the desired steam pressure, a first control circuit including a differentially connected amplifier device connected to receive the output of said integrating circuit, a positioning unit responsive to said first control circuit connected for controlling a fuel valve in response to output from said amplifier device, a second differentially connected amplifier device comprising a second control circuit having one input taken from said output of the first control circuit and a second input responsive to the output of said proportional and integrating circuit, a second positioning unit connected for response to said second control circuit and in control of air flow, a fuel oil pressure detecting transducer connected to a fuel supply to the boiler, an air flow sensing device connected to an air supply to the boiler the input of said first control circuit being responsively connected to said fuel oil pressure transducer and the input of said second control circuit being connected for response to the air flow sensing device and to the fuel oil pressure transducer.
 2. In a system according to claim 1 differentially connected amplifier means connected for response to a steam pressure requirement signal and supplying said signal to said proportional and integrating circuit for proportional effect on the output from said last-named circuit.
 3. In the system of claim 1, rapid switching means under control of a trip signal from a turbine system supplied by said steam boiler for supplying a time-derivative signal to said proportion and integrating circuit when the steam supply to said turbine engine system is shut off by a safety system.
 4. In a system according to claim 1, said differentially connected amplifiers comprising operational amplifiers connected for output according to the difference between input signals and said proportional and integrating circuit comprising an operational amplifier connected for producing a proportional and integrated signal output.
 5. In the system of claim 1, said first control circuit having said amplifier device connected for response to the output signal from said second control circuit by way of zener diode means to the output signal from the first control circuit according to sensed air flow below a set value.
 6. In the system of claim 1, said second control circuit having input to said amplifier device thereof derived from an input signal to said positioning unit controlling fuel delivered through RC network means to provide a differentiated signal.
 7. In the system of claim 1 means connected to said boiler for detecting oxygen content of flue gases and means responsive thereto for varying the operation of the flow control unit to reduce air flow according to oxygen detected, said means operating to provide an input to said second control circuit.
 8. In a system according to claim 7 said means for detecting oxygen comprising an integrator-connected operational amplifier having a feedback circuit including Zener diode means for limiting the magnitude of signal applied to the second control circuit.
 9. In a system according to claim 1, transistor amplifier means connected to the output for said control circuits to enhance the signals to said positioning units.
 10. In the system of claim 1, manually operable control signal generating means connected to each said control circuit, including further differentially connected operational amplifier means responsive to said manually operable means supplying input for said integrating circuit.
 11. In the system of claim 10, means connecting said manually operable means such that output from one said further operational amplifier means provides a gauge-operating signal and the other said further operational amplifier means provides input to said integrating means.
 12. In the system of claim 1, said second integrating circuit means for simulating a steam demand signal and generating a fuel control signal comprising amplifier means responsive to said output of said integrating circuit.
 13. In the system of claim 1, comparator-connected operational amplifier means connected responsiveLy to the output of said proportional and integrating circuit, and amplifier means connected for response to the output of said comparator-connected amplifier means, for supplying a rapid start or stop signal for a burner, and relay means responsively connected thereto to furnish start or stop actuation power.
 14. In the system of claim 1, amplifier means for controlling an actuation signal to a further positioning unit, being connected for response to output from said proportional and integrating circuit and supplying an actuating signal for a steam-dumping valve upon developing a predetermined output and a steam-dumping valve connected thereto. 